The Environmental Protection Agency’s pending global warming regulations are no “end run” around Congress, as many conservatives are charging. This time, Congress is being held hostage by its own laws.

The real story is the decades-long campaign by environmentalists to weave a legal web all but compelling the government to enact strict new climate change rules.

In 1970, before global warming was even on the radar map, Congress in the Clean Air Act gave the EPA the power to regulate air pollutants that damage “weather” and “climate” from automobiles and other moving pollution sources.

Members of Congress debating the law barely mentioned this language, according to a book about the law by environmental law professor Arnold Reitze. Meanwhile, a government report discussed the possibility that pollution could lead to another ice age.

It wasn’t until 1990 that the issue came to the forefront again, this time when Congress enacted a major update to the Clean Air Act. Then, some liberals in the Senate fought to require controls under the law on “greenhouse gases” thought to cause global warming. The provision was stripped from the bill in Conference Committee.

But in the last few years of the Clinton administration, the Carol Browner-led EPA issued a legal memo laying the groundwork for regulating global warming under the Clean Air Act’s existing language.

Years later, completely stymied by the Bush administration and Republicans in Congress, environmentalists took the memo and ran with it – in court.

In 2007, the Supreme Court sided with them, 5-4, in Massachusetts v. EPA. “Because greenhouse gases fit well within the Clean Air Act’s capacious definition of ‘air pollutant,’ we hold that EPA has the statutory authority to regulate the emission of such gases,” the court ruled.

That court battle was the real fight, and environmentalists already won, three years ago.

But the problem for the environmental community, President Obama, and, most importantly, the economy is this: using the Clean Air Act was only supposed to be a threat. The idea was, using the Clean Air Act for climate change was so heinously bad it would force industry and Republicans to come to the negotiating table.

“I’m the first person to say this is not a very effective means of addressing the problem,” said the Sierra Club’s David Bookbinder, a leading environmental strategist, in 2007, according to Environmental Health Perspectives.

“Our larger strategy is, we want legislation to curb emissions. No one is hiding the ball here,” said the Natural Resource Defense Council’s David Doniger, another top enviro lawyer, according to Inside EPA.

Well, that didn’t work. Obama tanked on a cap-and-trade climate change bill, and now the regulations are actually going forward.

The change in plans has environmentalists changing their tune. They launched a major campaign in past months to defend EPA regulations of global warming.

“Every line of evidence points to the same conclusion. Allowing EPA to do what it is legally required to do,” regulate climate change under the Clean Air Act, “will not cost us jobs or damage the economy. In fact, there’s every reason to believe the opposite,” said the NRDC’s Laurie Johnson in a blog post.

“Fears of agency ‘overreach’ are misplaced,” said the World Resources Institute in a report detailing how harmless the Clean Air Act regulations will be.

In fact, there are many problems the EPA faces in using the Clean Air Act.

First, the law was designed for pollutants like smog that accumulate in a given city or region. The law is actually implemented by states, who can individually fail to meet pollution reduction goals, thus becoming “out of attainment,” facing penalties.

Greenhouse gases are essentially evenly distributed across the globe. It hardly makes sense to hold individual states accountable for their greenhouse gas levels when every pollution source across the entire planet is contributing to that level.

Second, another major lever in the law is to require the best pollution-control technology on any newly built or upgraded facilities like factories and power plants.

No technology currently exists to “scrub” greenhouse gasses from emissions, so requiring the best technology is inherently limited, even illogical.

Third, enforcing the Clean Air Act typically means ensuring permanent pollution control technology is installed at a facility and properly working.

For climate change pollutants, since there is no control technology, the amount of pollution is basically a factor of how much output there is by a facility. This creates a huge, unique financial incentive for any given facility to cheat on a greenhouse gas cap, since more production is more revenue. It will be much harder to track for EPA agents than typical air pollutants.

Fourth, the EPA has already had to significantly bend the letter of the law to avoid bureaucratic Armageddon.

The Clean Air Act says a given pollution source comes under EPA oversight if it is emitting more than 100 or 250 tons per year. To avoid capturing over six million new facilities under regulation, including nearly four million single-family homes (a 40,594 percent increase that would presumably ensnare Al Gore’s mansion), the EPA issued a regulation which puts the threshold at 100,000 tons of pollution per year.

Whether that rather sizable legal leap withstands judicial scrutiny is an open question. If it does not, the result would be complete meltdown, as the EPA freely concedes.

Fifth, as EPA Administrator Lisa Jackson has admitted, the EPA regulations will have little or no impact on global average temperatures. There are no Clean Air Act regulations on India or China, and greenhouse gas-emitting manufacturing can be outsourced.

In April, the EPA estimated its climate change regulations for automobiles and other “mobile” sources would reduce the average global temperature by 0.006 to 0.0015 degrees Celsius over the next 90 years.

A series of climate change torts suits alleging violations under common law are working their way up the court system. The Supreme Court has yet to rule on the issue, but the potential liability to industry is huge and creating major uncertainty in the market.

They’ve also sued for action on global warming under the Endangered Species Act.

Each of these seemingly far-fetched lawsuits is designed to create more and more uncertainty and therefore more and more incentive for industry and Republican opponents of cap-and-trade to buckle under pressure.

Whatever one’s views on their ends, a disciplined army of environmental lawyers appears to be winning this war.